Tutorials - Carbohydrate metabolism: Citric Acid Cycle

16 important questions on Tutorials - Carbohydrate metabolism: Citric Acid Cycle

What is the final output (end products) of the CAC?

The most important outputs of the CAC are the reduced coenzymes FADH2 and NADH

How much product is created each time the CAC is completed?

Three NADH and one FADH2

What product is created that makes the CAC a cyclical process?

Oxaloacetate created in the final step (step 8) and then used as a reactant in step 1 of the next CAC makes the CAC a cyclical process
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Where does the input required for the CAC come from?

Acetyl CoA can come from the breakdown of carbohydrate (glycolysis), lipid (beta oxidation) or protein (transamination)

What is the final output of the CAC used for?

Electron rich coenzymes NADH and FADH2 go to the electron transport chain, where they off-load their electrons to begin the electron transport chain (ETC) process

Why is it important for us to perform the CAC?


CAC produces electron rich coenzymes NADH and FADH2 which are needed to provide electrons to the electron transport chain, and which are then used to create ATP

How do allosteric enzymes work?

Positive and negative regulators bind to the enzyme’s regulatory binding site to increase or decrease the activity of the enzyme respectively

What is the main source of Oxaloacetate?

Malate from the last step, step 8, of the CAC

What is an alternative source of Oxaloacetate?

Pyruvate

How is the coenzyme NAD+ used in step 4 of the CAC?

CoA loses a hydrogen atom to NAD+ which becomes NADH, and this facilitates the attachment of CoA to the alpha Ketogluterate, generating Succinyl CoA

How is the coenzyme NAD+ used in step 8 of the CAC?

One of the alcohol groups of malate is oxidised to a ketone group by losing two hydrogen atoms to NAD+ which becomes NADH, resulting in the compound becoming oxaloacetate

How is the coenzyme FAD used in step 6 of the CAC?

The reactant succinate loses two hydrogen atoms to FAD which becomes FADH2 and the two central carbon atoms create an additional carbon-carbon bond, which results in the formation of a double carbon-carbon bond creating the compound fumarate

What is oxaloacetate used for after step 8 of the CAC?

To begin another cycle of the CAC as oxaloacetate is one of the two inputs required for step 1 of the CAC along with Acetyl CoA

How many NADH and FADH2 molecules are produced, respectively, during one turn of the citric acid cycle?

Three NADH and one FADH2

What is the correct designation for the reduced form of coenzyme FAD?

FADH2

In which process is glycogen is converted to glucose?

Glycogenolysis

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